In the quest for sustainable energy solutions, thermoelectric materials are emerging as a promising avenue for waste heat recovery and cooling applications. These materials can convert temperature differences directly into electrical energy, offering a clean and efficient way to harness otherwise lost heat. Now, a breakthrough in this field comes from researchers at the Institute of Materials Research at the German Aerospace Center (DLR) in Cologne, Germany. Led by Amandine Helt, the team has developed a novel method for contacting thermoelectric materials, paving the way for more efficient and commercially viable devices.
The study, published in the journal Science and Technology of Advanced Materials, focuses on the thermoelectric material α-MgAgSb, a tellurium-free alternative to traditional bismuth telluride. This material has shown impressive performance, with a high figure of merit (zTmax = 1.3), making it suitable for applications between room temperature and 573 K. However, to optimize the performance of thermoelectric devices, it is crucial to minimize the electrical contact resistance between the material and the electrodes.
Helt and her team investigated the use of MgCuSb as an electrode for contacting pre-compacted pellets of MgAgSb. “We wanted to see if MgCuSb could provide a low-resistance contact while maintaining the integrity of the thermoelectric material,” Helt explained. The researchers systematically varied the sintering temperature, duration, and pressure to analyze the microstructural and electrical properties of the interfaces formed.
The results were promising. The team observed the formation of an interdiffusion layer of Ag3Sb, but the contact resistance remained consistently low, below 10 μΩ cm2. Moreover, the Seebeck coefficient measurements indicated a change in carrier concentration near the interface, suggesting interdiffusion processes between MgAgSb and MgCuSb. “This interdiffusion is actually beneficial,” Helt noted, “as it helps to create a strong mechanical contact without any cracks at the interface.”
One of the most significant findings was the successful two-step contacting of MgAgSb, a first in the field. The researchers applied MgCuSb as an electrode on pre-compacted MgAgSb samples, resulting in a very low electrical contact resistance of less than 7 µΩ cm2. This resistance represents less than 5% of the total leg resistance, a remarkable achievement that could greatly enhance the efficiency of thermoelectric devices.
The implications of this research are far-reaching. The ability to contact pre-compacted thermoelectric materials allows for better control of the leg length and thus device performance. This could lead to more efficient waste heat recovery systems in industrial processes, automotive applications, and even in consumer electronics. As Helt puts it, “This is a step forward towards module fabrication, enabling better control and optimization of thermoelectric devices.”
The energy sector is always on the lookout for innovative solutions to improve efficiency and reduce environmental impact. Thermoelectric materials, with their ability to convert waste heat into electricity, offer a compelling opportunity. The work by Helt and her team at DLR brings us closer to realizing the full potential of these materials, making thermoelectric devices more practical and commercially attractive.
As the world continues to seek sustainable energy solutions, advancements in thermoelectric technology will play a crucial role. The research published in Science and Technology of Advanced Materials, which translates to “Science and Technology of Advanced Materials” in English, highlights the importance of material science in driving innovation. With continued research and development, thermoelectric devices could become a staple in our quest for a more energy-efficient future.